1. Field of the Invention
The invention relates to an exhaust gas line section for supplying a liquid additive into an exhaust gas treatment device. An exhaust gas line section of this type can be arranged in an exhaust gas line or in an exhaust gas treatment device and is flowed through by the exhaust gas during operation of an internal combustion engine connected to the exhaust gas line or to the exhaust gas treatment device. A liquid additive can be supplied to an exhaust gas flow by way of the described exhaust gas line section.
2. Related Art
Exhaust gas treatment devices to which a liquid additive is supplied are widespread. In exhaust gas treatment devices of this type, the exhaust gas purification method of selective catalytic reduction (SCR) is implemented, for example. In the method, nitrogen oxide compounds in the exhaust gas are reduced with the aid of a reducing agent. Ammonia is used, in particular, as a reducing agent. Ammonia is often not supplied directly to an exhaust gas treatment device, however, but rather in the form of a reducing agent precursor solution. The reducing agent precursor solution is a liquid additive which can be supplied to an exhaust gas flow by way of the described exhaust gas line section.
Urea-water solution is used particularly frequently as a liquid additive for the exhaust gas purification. A urea-water solution with a urea content of 32.5% is available under the trade name AdBlue®.
During the metering, i.e., injection, of liquid additive to the exhaust gas treatment device, it is a problem that the liquid additive very readily forms deposits in the exhaust gas treatment device. For example, the urea-water solution has to evaporate rapidly during the supply to an exhaust gas treatment device, in order that no crystalline urea particles are formed. Moreover, a homogeneous distribution of the liquid additive in the exhaust gas flow is aimed for during the supply. By way of a homogeneous distribution of the liquid additive, the formation of deposits can be avoided because a spatially restricted enrichment of the exhaust gas with liquid additive does not occur. Local enrichment can lead to the formation of relatively large additive droplets, which do not evaporate or evaporate only with difficulty and increase the formation of deposits.
In order to avoid deposits, the liquid additive should not, in particular, come into contact with an outer wall of the exhaust gas treatment device during the supply. The outer wall is often directly in contact with the surroundings, with the result that it is loaded with the external temperature from an outer side. Accordingly, the outer wall is often very much colder than other regions of the exhaust gas treatment device, which are spaced apart from the outer wall. Liquid additive can therefore condense on the wall of the exhaust gas line or cannot condense (rapidly enough) and can thus frequently lead to deposits (which cannot be removed or can be removed only with difficulty).